<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .content{
           margin: 0px;
           padding: 0px;
           display: flex;
           width: 500px;
           height: 200px;

        }
        .con{
            background-color: red;
            flex-grow: 1;
        }
        .cons{
            background-color: blue;
            flex-grow: 1;
        }
        .const{
            background-color: green;
            flex-grow: 1;
        }
    </style>
</head>
<body>
    <div class="content">
        <div class="con"></div>
        <div class="cons"></div>
        <div class="const"></div>
    </div>
</body>
</html>